Progress sync - surefish/koreader GitHub Wiki
The "Progress sync" plugin can synchronize reading progress of the same document across different koreader devices. You need to create an account on one device by registering in the "Register/Login" menu of the plugin and login on other devices. If "Auto sync" is checked, synchronization will be performed when a document is opened and closed. You can also manually synchronize the reading progress by tapping the "Sync now".
This plugin does not send file name or any file content to the koreader sync server. And all data transferred between the "Progress sync" plugin and the sync server are secured by HTTPS (Hypertext Transfer Protocol Secure) connections.
You need to have a copy of the book/document on both the device you started reading on and on the KOReader device you want to continue reading on. You can use the KOReader Zsync plugin to "Publish" the book, so that your other KOReader equipped devices can "Subscribe" and place a copy in the folder you select by a long press and confirmation.